Deposits of valuable fluids, such as crude oil, natural gas and even water, frequently occur in geologic formations having limited permeability. Although the initial perforating of the sides of an oil well typically opens up this type of deposit for initial exploitation, the well may soon experience a drop in production and require further treatment. To address this situation, a number of different fracturing techniques have been developed including explosive fracturing, hydraulic fracturing and high energy gas fracturing (HEGF). Each of these techniques is designed to fracture the underground geologic formation, thereby increasing permeability.
HEGF appears to have an advantage over the other fracturing techniques when certain conditions exist in a well. Test observations have shown that HEGF can create several radially extending fractures, thereby increasing the chance of significantly increasing permeability of nearby rock.
One type of HEGF uses a propellant that must be kept dry and contained during combustion. In this version, a strong container bearing a charge of propellant (i.e. a low explosive) is lowered into a partially liquid filled well and the propellant is ignited. The container keeps the charge dry and constrains it to obtain the full explosive force.
One type of propellant container that has been used is a steel tube defining a series of apertures, each capped. When the propellant is ignited the caps are blown off and the propellant, now in gaseous form, pours out of the apertures and fractures the rock sides of the well, thereby creating fissures through which oil can flow.
Unfortunately, the protruding caps made this mechanism too thick to fit into some narrow wells. Wells that are too narrow to accept the 3.375 inch profile of the original HGEF device offered previously are found in Mexico and other developing countries, and in the United States, when a portion of a tube mechanism in a well (associated with a sucker pump) the upper part of well cannot be removed, or is too long to be removed economically, it is impossible to use a 3.375 inch profile device. Narrowing the tube to permit clearance for the caps reduces the volume of the tube to the point where the effectiveness is reduced. The thickness of the steel is necessary to resist the expansive forces of the propellant, once ignited.